muckraker

noun

1. (US)One who investigates and exposes issues of corruption that often violate widely held values; e.g. one who exposes political corruption or the poor conditions in prisons.

   “The paper gave a start to the theater critic Hilton Als and the novelist Colson Whitehead, both recipients of the Pulitzer Prize. Its resident muckraker, Wayne Barrett, took aim at New York developers and politicians for nearly 40 years, and his obsessive work on Donald J. Trump has become a resource for reporters covering the president today.”

2. (US, historical)One of a group of American investigative reporters, novelists and critics of the Progressive Era (the 1890s to the 1920s).

   “"Oh, in many ways. There are two classes of people who are not welcomed on the Canal Zone—magazine writers and applicants for positions who have political influence back of them. The former are regarded as muckrakers, the latter as spies."”

   “"Lady," says he, "the goil's nutty! You got a bughouse patient on your bands! This here talk about the white-slave traffic, ma'am… it's all the work o' these magazine muckrakers!"”

3. (British, derogatory)A sensationalist, scandalmongering journalist, one who is not driven by any social principles.